Research seven kilometres deep

Photos: Field work Anak Agung Gede Indraningrat, Curacao

Sponges are simple multicellular animals attached to the seabed. There are thousands of different species and they can be found both in fresh and salt water. Special for sponges is that they filter thousands of times their own weight in water every day to provide themselves with food.

Symbiosis with bacteria

Scientists examine sponges because they live together with bacteria. In this symbiosis substances are produced that may also be of interest for applications ashore, for example as a possible antibiotic. Each species of sponge carries its own bacteria, says microbiologist Detmer Sipkema of Wageningen University, specialized in sponge research. "People also have bacteria in their bodies. More than you have cells, with a total weight of about one kilogram. For sponges the amount of bacteria add up to half their weight. No other animal carries this many bacteria and hence this many bioactive substances."

The deep deep-ocean

However, still little is known about the ecology of the sponge. Sipkema is researching this together with colleagues; before mainly in the Eastern Scheldt, nowadays all over the world. This fall, PhD-student Anak Agung Gede Indraningrat from Wageningen University, who is financially supported by the Indonesia Endowment Fund for Education (LPDP), got the opportunity to gather sponge samples in the Caribbean. He was able to dive to a depth of approximately 250 meters by using an advanced small submarine. The 250 metres is the limit to which light just penetrates in the ocean - important because much of the marine life is dependent on sunlight. "This will provide us with information on the effect of depth on the occurrence of micro-organisms, and, hopefully, also about the constituents for antibiotics," says Indraningrat, who has just returned from Curacao.

Some organisms are able to live in the dark, though. Sipkema: "Divers usually go no deeper than eighteen meters, and advanced divers as deep as sixty meters – where they can stay only shortly. Unfortunately we know the surface of the moon better than the bottom of the ocean. The deeper we search, the more likely we thus are to encounter something unknown."

Cycle of elements

In the new European project SPONGES, Sipkema will research sponges at 7,000 m depth at the Mid-Atlantic Ridge, in the middle of the Atlantic Ocean where strata meet. For this research the researcher will use an underwater robot (remotely operated vehicle or ROV) that can be directed by remote control from a boat or platform. The research is conducted in this area because of the hydrothermal veins; here, black "water clouds" rise from the seabed. "Thanks to the substances in these clouds, life is also possible this deep. We will examine the microorganisms in the sponges living down there, the substances they produce, and their role in the cycles of elements such as nitrogen and silicon. This knowledge is important because there are business parties that want to start extracting metals or energy from these clouds. Then you have to know what this would mean for the ecology and the natural cycles."

Bioactive molecules

Sipkema hopes to study the found microbes in the lab for the biologically active molecules they produce. Also genetic analysis has his interest. "Because this too can give an indication of the potential of sponges and their microorganisms in the search for new medicines." The mapping of the genes already takes place for sponges living in more shallow places, as part of the major and ongoing EU project BluePharmTrain, coordinated by Wageningen UR, and a Dutch Wageningen project together with businesses (BE-Basic).

Animal scientists and bioprocess technologists of Wageningen University are involved in other parts of SPONGES. They will look at the possible effects of global warming on deep-ocean ecosystems and the possibility of using the silicon skeletal structures of sponges for biomedical applications.